JP6689273B2 - Rubber composition - Google Patents

Description

  The present invention is particularly applicable to icy or black ice covered ground surfaces not provided with studs (also known as studless tires) while at least maintaining or even improving grip when wet. It relates to a rubber composition that can be used as a tread for a rotatable "winter tire".

  More particularly, it relates to treads for winter tires that are particularly suitable for rotation under "melting ice" conditions, which typically occur in a temperature range between -5 ° C and 0 ° C.

  It should be particularly noted that, in such a range, the pressure of the tires during the passage of the vehicle leads to a surface melting of the ice, which is covered by a thin film of water on the ice melt which is detrimental to the grip of these tires. Is.

  WO 2010/0009850 and WO 2012/052331 filed by the applicant contain them under ice-melting conditions without inconvenience to the properties and history of reinforcement. It describes a specific rubber composition capable of producing effective surface microroughness with specific fine particles, which is capable of improving the grip of the tread and the tire on ice.

  These microparticles protruding on the surface of the tread are known claw functions without the disadvantage of abrasive action on the surface of the ground itself and without significantly worse road behavior on dry ground. ) Exert. Then, after gradual release from the rubber matrix, they release tiny cavities that serve as storage volumes and as channels for draining the water film at the surface of the ice; under these conditions, The contact between the tread surface and the ice is no longer smooth, thus improving the coefficient of friction.

  It is a tire manufacturer's constant goal to further improve grip on ice, especially on melted ice, without compromising one of the essential tire performances, grip on wet.

  In the continuation of the study, we have at least maintain or even improve wet grip, which is the grip on wet road surfaces, while tread and tires comprising them under ice-melting conditions on ice. We have found a new rubber composition comprising a specific combination of plasticizer and water-soluble sulphate particles, which makes it possible to improve the grip.

  Accordingly, a first subject of the invention is between at least 20 phr and at least 160 phr comprising at least a diene elastomer, between 50 phr and 150 phr of a reinforcing filler and more than 10 phr and less than 80 phr of vegetable oil. A rubber composition comprising a plasticizer and between 2 and 40 phr of fine particles of an alkali metal or alkaline earth metal water-soluble sulfate.

  Further, the aspects of the present invention can be as follows.

[1] At least
A diene elastomer,
-Reinforcing filler between 50 phr and 150 phr,
Between 20 and 160 phr of plasticizer, comprising greater than 10 phr and less than 80 phr of vegetable oil;
A rubber composition comprising between 2 phr and 40 phr of fine particles of water-soluble sulfate of an alkali metal or alkaline earth metal.

[2] The rubber composition according to [1], wherein the content of the vegetable oil is more than 10 phr and less than 70 phr.

[3] The vegetable oil is linseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, turnip seed oil, castor oil, millet oil, pine oil, sunflower oil, palm oil, olive oil, coconut oil, peanut oil, grape seed The rubber composition according to [1] or [2], which is selected from the group consisting of oils and mixtures thereof.

[4] The rubber composition according to [3], wherein the vegetable oil is sunflower oil.

[5] The rubber composition according to any one of [1] to [4], wherein the fatty acid from which the vegetable oil is derived contains oleic acid in a weight fraction of 60% or more.

[6] The fine particles are both measured by laser diffractometry according to ISO standard 13320-1, and have the following relationship:
−50 μm <D50 <150 μm;
-0.50 <span <1.50;
(In the formula,
-D50 is the median particle size by volume corresponding to 50% of the cumulative distribution obtained from the volume particle size distribution;
-Span = (D90-D10) / D50; and-D10 and D90 are particle sizes corresponding to 10% and 90% by volume of the cumulative particle distribution, respectively).
The rubber composition according to any one of [1] to [5], which has a median particle size and a volume particle size distribution width by volume that satisfy the above conditions.

[7] The rubber composition according to any one of [1] to [6], wherein the content of the fine particles is between 2 phr and 30 phr.

[8] The rubber composition according to any one of [1] to [7], wherein the alkali metal or the alkaline earth metal is selected from the group consisting of sodium, potassium, magnesium, calcium and a mixture thereof. object.

[9] The rubber composition according to any one of [1] to [8], wherein the water-soluble sulfate is selected from the group consisting of magnesium sulfate, potassium sulfate and a mixture thereof.

[10] The rubber composition according to any one of [1] to [9], wherein the water-soluble sulfate is magnesium sulfate.

[11] The rubber according to any one of [1] to [10], wherein the diene elastomer is selected from the group consisting of natural rubber, synthetic polyisoprene, polybutadiene, butadiene copolymer, isoprene copolymer and mixtures thereof. Composition.

[12] The rubber composition according to [11], which comprises more than 50 phr of natural rubber or synthetic polyisoprene.

[13] The rubber composition according to [11], which comprises more than 50 phr of polybutadiene having a content of cis-1,4 bond higher than 90%.

[14] The rubber composition according to any one of [1] to [13], wherein the reinforcing filler contains more than 60 phr of carbon black.

[15] The rubber composition according to any one of [1] to [14], wherein the reinforcing filler contains a reinforcing inorganic filler in an amount of more than 70 phr.

[16] The rubber composition according to any one of [1] to [15], wherein the content of the total reinforcing filler is between 60 phr and 120 phr.

[17] The rubber composition according to any one of [1] to [16], wherein the content of the plasticizer is between 30 phr and 120 phr.

[18] The plasticizer according to any one of [1] to [17], further comprising a compound selected from the group consisting of a hydrocarbon resin, a liquid plasticizer other than the vegetable oil, and a mixture thereof. The rubber composition described.

[19] The rubber composition according to [18], wherein the hydrocarbon resin has a Tg higher than 20 ° C.

[20] The hydrocarbon resin is a cyclopentadiene homopolymer or copolymer resin, a dicyclopentadiene homopolymer or copolymer resin, a terpene homopolymer or copolymer resin, a C5 fraction homopolymer or copolymer resin, a C9 fraction homopolymer or copolymer resin. The rubber composition according to [18] or [19], which is selected from the group consisting of an alpha-methylstyrene homopolymer or copolymer resin, and a mixture of these resins.

[21] The rubber composition according to any one of [18] to [20], wherein the content of the hydrocarbon resin is between 3 phr and 60 phr.

[22] The liquid plasticizer other than the vegetable oil may be polyolefin oil, naphthenic oil, paraffin oil, Distillate Aromatic Extracts (DAE) oil, Medium Extracted Solvents (MES) oil, Treated Distillate Aromatic Erastic, Erastic, Erastic, Eras. (RAE) oil, Treated Residual Aromatic Extracts (TRAE) oil, Safety Residual Aromatic Extracts (SRAE) oil, mineral oils, ether plasticizers, ester plasticizers, phosphate plasticizers, sulfonate plasticizers and mixtures thereof. Written in [18] Of the rubber composition.

[23] The rubber composition according to [22], wherein the content of the liquid plasticizer is less than 20 phr.

[24] Use of the composition according to any one of [1] to [23] for producing a tread for a pneumatic tire.

[25] A tread for a pneumatic tire, which comprises the composition according to any one of [1] to [23].

[26] A pneumatic tire comprising the tread described in [25].

  Another subject of the invention is the use of such rubber compositions in the manufacture of tire treads intended for new tires or for the regeneration of worn tires.

  Another subject of the invention is these treads and these tires themselves, which comprise a rubber composition according to the invention.

  The tire according to the invention is chosen in particular from passenger vehicles, including 4x4 (four-wheel drive) vehicles and SUV (sports utility vehicle) vehicles, two-wheeled vehicles (especially motorcycles), and also especially vans and heavy-duty vehicles. It is intended to be equipped on industrial vehicles (ie subways, buses or heavy road vehicles (trucks, tractors, trailers), or off-road vehicles such as agricultural vehicles or earthmoving machines).

  The invention and its advantages will be readily understood in view of the following description and examples.

  All percentages given herein are weight percentages, unless stated otherwise. Further, any interval of values indicated by the assertion "between a and b" represents a range of values that extends from above a to below b (ie, limits a and b are excluded), In contrast, any interval of values indicated by the expression "ab" means a range of values that extends from a to b (i.e., the exact limits a and b are included).

  The rubber composition of the present invention is based on at least a diene elastomer, a reinforcing filler, a plasticizer comprising vegetable oil, and microparticles of water-soluble sulfate of an alkali metal or alkaline earth metal component, which are Described in detail.

  The expression "based on" means in the present application that some of the components react together, at least in part, during the various production stages of the composition, in particular during vulcanization (curing). Should be understood as meaning a composition comprising a mixture of the various components used and / or the reaction products, which are or are intended to react together.

Diene Elastomer A "diene" elastomer (or "rubber", the two terms are considered to be synonymous) is a diene monomer (which may be conjugated or conjugated) in a known manner, at least in part. Should be understood as meaning elastomers (one or more being understood) (ie homopolymers or copolymers) obtained from monomers having two carbon-carbon double bonds which cannot be is there.

  These diene elastomers can be divided into two categories in a known manner: “essentially unsaturated” and “essentially saturated”. For example, butyl rubbers, such as EPDM-type diene and α-olefin copolymers, are low or very low, of essentially saturated diene elastomers having a diene-derived unit content that is always less than 15% (mol%). Belong to a category. In contrast, an essentially unsaturated diene elastomer means a diene elastomer obtained, at least in part, from a conjugated diene monomer having a unit content of diene-derived (conjugated diene) greater than 15% (mol%). Understood as a thing. In the category of "essentially unsaturated" diene elastomers, "highly unsaturated" diene elastomers mean, in particular, diene elastomers having a unit content of diene-derived (conjugated diene) of more than 50%. To be understood.

  At least one highly unsaturated diene elastomer, especially a diene elastomer selected from the group consisting of polybutadiene (BR), synthetic polyisoprene (IR), natural rubber (NR), butadiene copolymer, isoprene copolymer and mixtures of these elastomers. Is preferably used. Such copolymers are selected from the group consisting of butadiene / styrene copolymer (SBR), isoprene / butadiene copolymer (BIR), isoprene / styrene copolymer (SIR), isoprene / butadiene / styrene copolymer (SBIR) and mixtures of these copolymers. More preferably.

  Suitable elastomers are polybutadienes, in particular those having a 1,2-unit content of between 4% and 80%, or those having a cis-1,4-unit content of more than 80%, polyisoprene. A butadiene / styrene copolymer, in particular a styrene content of between 5% and 50% by weight, more particularly between 20% and 40% by weight, of 1,2% of the butadiene component of between 4% and 65%. With a bond content and a trans-1,4-bond content between 20% and 80%, a butadiene / isoprene copolymer, in particular an isoprene content between 5% and 90% by weight and -40 Having a glass transition temperature ("Tg", measured according to ASTM D 3418 (1999)) of -80 to -80 ° C, or isoprene / styrene copolymer, especially 5% by weight And a styrene content between 50 and 50% by weight and a Tg between -25 ° C and -50 ° C.

  In the case of butadiene / styrene / isoprene copolymers, a styrene content of between 5 and 50% by weight, more particularly between 10 and 40% by weight, between 15 and 60% by weight, In particular, an isoprene content between 20% and 50% by weight, a butadiene content between 5% and 50% by weight, more particularly between 20% and 40% by weight, 4% and 85%. 1,2-unit content of the butadiene component between 6% and 80%, trans-1,4-unit content of the butadiene component between 6% and 80%, between 1% of the isoprene component between 5% and 70%. 2- and 3,4-unit content, and those having a trans-1,4-unit content of the isoprene component of between 10% and 50%, more commonly -20 ° C and -70 ° C. Any butadiene / s having a Tg between Len / isoprene copolymers are particularly suitable.

  According to a particularly preferred embodiment of the present invention, the diene elastomer is from the group consisting of natural rubber, synthetic polyisoprene, polybutadiene having a cis-1,4 bond content higher than 90%, butadiene / styrene copolymers and mixtures thereof. To be selected.

  More particularly and according to a preferred embodiment, the diene elastomer used is predominantly, ie greater than 50 phr natural rubber (NR) or synthetic polyisoprene (IR) (“phr” being 100 parts elastomer). It should be noted that it means parts by weight per unit). More preferably, the natural rubber or synthetic polyisoprene is then used as a blend with polybutadiene (BR), which preferably has a cis-1,4 bond content higher than 90%.

  According to another particularly and preferred embodiment, the diene elastomer used is predominantly polybutadiene (BR), ie with more than 50 phr having a cis-1,4 bond content higher than 90%. More preferably, the polybutadiene is then used as a blend with natural rubber or synthetic polyisoprene.

  According to another especially and preferred embodiment, the diene elastomer used is a binary blend of NR (or IR) and BR or a ternary blend of NR (or IR), BR and SBR. . Preferably, for such blends, the composition comprises between 25 phr and 75 phr NR (or IR) and between 75 phr and 25 phr BR and comprises less than 30 phr, especially less than 20 phr of a third. The elastomer (three-component blend) may or may not be related. This third elastomer is preferably an SBR elastomer, especially a solution SBR (“SSBR”). Even more preferably, in such a blend, the composition comprises 35 to 65 phr NR (or IR) and 65 to 35 phr BR. The BR used is preferably a BR having a cis-1,4 bond content higher than 90%, more preferably higher than 95%.

  Synthetic elastomers other than diene elastomers, indeed polymers other than elastomers, for example thermoplastic polymers, may be combined in minor amounts with the diene elastomers of the compositions of the invention.

Reinforcing fillers Any type of reinforcing fillers known for their ability to reinforce rubber compositions that can be used in the manufacture of tires, for example, organic fillers such as carbon black, reinforcing inorganic fillers such as silica. , May be used in combination with coupling agents in a known manner.

  Such reinforcing fillers typically consist of nanoparticles whose average diameter (by weight) is less than 500 nm, generally between 20 nm and 200 nm, particularly preferably between 20 nm and 150 nm.

  All carbon blacks customarily used in tire treads, in particular HAF, ISAF or SAF type blacks (“tire grade” blacks), are suitable as carbon blacks. In particular, among the latter, for example, 100, 200 or 300 series (ASTM grade) reinforced carbon blacks such as N115, N134, N234, N326, N330, N339, N347 or N375 black may be mentioned. The carbon black may already be incorporated into the isoprene elastomer, for example in the form of a masterbatch (see for example WO 97/36724 or WO 99/16600).

  Examples of organic fillers other than carbon black are described in WO 2006/069792, WO 2006/069793, WO 2008/003434 and WO 2008/003435. Mention may be made of functionalized polyvinyl organic fillers such as

  The term "reinforcing inorganic filler" is also known herein as "white filler" or "transparent filler" in contrast to carbon black, regardless of its color and its origin (natural or synthetic). It should be understood as meaning any inorganic or mineral filler. It is possible on its own to reinforce a rubber composition intended for the production of tires, by means other than by means of intermediate coupling agents, in other words ordinary tire grade carbon black and its reinforcing role. Can be replaced in. Such fillers are generally characterized in the known manner by the presence of hydroxyl (—OH) groups on their surface.

  Silica-type mineral fillers, especially silica (SiO2), or aluminous-type mineral fillers, especially alumina (Al2O3), are particularly suitable as reinforcing inorganic fillers. The silica used can be any reinforcing silica known to the person skilled in the art, in particular a BET surface area and a CTAB specific surface area of less than 450 m2 / g, preferably between 30 and 400 m2 / g, especially between 60 m2 / g and 300 m2 / g. Can be any precipitated or pyrogenic silica. Highly dispersible (“HD precipitated silicas”) include, for example, Ultrasil 7000 and Ultrasil 7005 silica from Evonik; Zeosil 1165MP, 1135MP and 1115MP silica from Rhodia; Hi-Sil EZ150G silica from PPG; Zeopol 15 from Huber. , 8745 or 8755 silica may be mentioned. Examples of reinforced aluminas are "Baikalox A125" or "Baikalox CR125" alumina from Baikowski, "APA-100RDX" alumina from Condea, "Aluminoxid C" alumina from Degussa or "AluminoxidC" from Sumitomo Chemical-C01A5C. Alumina may be mentioned.

  Preferably, the content of total reinforcing filler (carbon black and / or reinforcing inorganic filler) is between 60 phr and 120 phr, especially between 70 phr and 100 phr.

  According to a particular embodiment, the reinforcing filler comprises predominantly carbon black; in such cases the carbon black is preferably in combination with or without a small amount of reinforcing inorganic filler such as silica. Is present in a content higher than 60 phr.

  According to another particular embodiment, the reinforcing filler comprises predominantly an inorganic filler, especially silica; in such a case the inorganic filler, especially silica, in combination with a minor amount of carbon black, or Uncombined, preferably present in a content greater than 70 phr; carbon black, when present, is preferably used in less than 20 phr, more preferably less than 10 phr (eg, between 0.1 phr and 10 phr). .

  Independent of the first aspect of the invention, namely the search for optimized grips on melt ice, the main use of reinforcing inorganic fillers such as silica is from the perspective of grips on wet or snow-covered ground surfaces. Is also advantageous.

  According to another possible embodiment of the invention, the reinforcing filler comprises a blend of carbon black and a small amount of a reinforcing inorganic filler such as silica, in which case the inorganic filler, in particular silica. The content and the content of carbon black are preferably between 25 and 75 phr, respectively, and more particularly between 30 and 50 phr, respectively.

  To couple the reinforcing inorganic filler to the diene elastomer, in a well-known manner, a satisfactory bond of chemical and / or physical properties is provided between the inorganic filler (its particle surface) and the diene elastomer. At least a bifunctional coupling agent (or binder) intended to be used. In particular, difunctional organosilanes or polyorganosiloxanes are used.

（式中、
Ｒ１基は、置換されていないかまたは置換されており、かつ互いに同一かまたは異なるものであって、Ｃ１〜Ｃ１８アルキル、Ｃ５〜Ｃ１８シクロアルキルまたはＣ６〜Ｃ１８アリール基（好ましくはＣ１〜Ｃ６アルキル、シクロヘキシルまたはフェニル基、特にＣ１〜Ｃ４アルキル基、より特にメチルおよび／またはエチル）を示し；
Ｒ２基は、置換されていないかまたは置換されており、かつ互いに同一かまたは異なるものであって、Ｃ１〜Ｃ１８アルコキシルまたはＣ５〜Ｃ１８シクロアルコキシル基（好ましくは、Ｃ１〜Ｃ８アルコキシルおよびＣ５〜Ｃ８シクロアルコキシル基から選択された基、より好ましくはＣ１〜Ｃ４アルコキシル基、特にメトキシルおよびエトキシルから選択された基）を示す）の１つに相応する］は、以下の定義に限定されることなく、特に適している。さらに詳細には、シランポリスルフィドの例としては、例えば、ビス（３−トリメトキシシリルプロピル）またはビス（３−トリエトキシシリルプロピル）ポリスルフィドなどのビス（（Ｃ１〜Ｃ４）アルコキシ（Ｃ１〜Ｃ４）アルキルシリル（Ｃ１〜Ｃ４）アルキル）ポリスルフィド（特にジスルフィド、トリスルフィドまたはテトラスルフィド）が挙げられる。特に、これらの化合物の中でも、式［（Ｃ２Ｈ５Ｏ）３Ｓｉ（ＣＨ２）３Ｓ２］２のＴＥＳＰＴと略称されるビス（３−トリエトキシシリルプロピル）テトラスルフィド、または式［（Ｃ２ＨＳＯ）３Ｓｉ（ＣＨ２）３Ｓ］２のＴＥＳＰＤと略称されるビス（トリエトキシシリルプロピル）ジスルフィドを使用する。また、好ましい例としては、国際出願第０２／０８３７８２号パンフレット（または米国特許出願公開第７２１７７５１号明細書）に記載されているような、ビス（モノ（Ｃ１〜Ｃ４）アルコキシルジ（Ｃ１〜Ｃ４）アルキルシリルプロピル）ポリスルフィド（特に、ジスルフィド、トリスルフィドまたはテトラスルフィド）、より特に、ビス（モノエトキシジメチルシリルプロピル）テトラスルフィドも挙げられる。 In particular, for example, in WO 03/002648 (or US Patent Application Publication No. 2005/016651) and WO 03/002649 (or US Patent Application Publication 2005/016650). Silane polysulfides, referred to as "symmetrical" or "asymmetrical", are used, as described, depending on their particular structure. A "symmetrical" silane polysulfide corresponding to general formula (I) below:
(I) ZA-Sx-AZ
[In the formula (I),
x is an integer of 2 to 8 (preferably 2 to 5);
A is a divalent hydrocarbon group (preferably a C1-C18 alkylene group or a C6-C12 arylene group, more particularly a C1-C10, especially a C1-C4 alkylene group, especially propylene);
Z is the following chemical formula:

(In the formula,
The R1 groups are unsubstituted or substituted and identical or different from one another and are C1-C18 alkyl, C5-C18 cycloalkyl or C6-C18 aryl groups (preferably C1-C6 alkyl, A cyclohexyl or phenyl group, especially a C1-C4 alkyl group, more particularly methyl and / or ethyl);
The R2 groups are unsubstituted or substituted and identical or different from one another and are C1-C18 alkoxyl or C5-C18 cycloalkoxyl groups (preferably C1-C8 alkoxyl and C5-C8 cyclol). A group selected from alkoxy groups, more preferably a C1-C4 alkoxy group, especially a group selected from methoxyl and ethoxyl)) corresponds to, but is not limited to, the following definitions: Are suitable. More specifically, examples of the silane polysulfide include, for example, bis ((C1-C4) alkoxy (C1-C4) alkyl such as bis (3-trimethoxysilylpropyl) or bis (3-triethoxysilylpropyl) polysulfide. Mention may be made of silyl (C1-C4) alkyl) polysulphides (especially disulfides, trisulphides or tetrasulphides). In particular, among these compounds, bis (3-triethoxysilylpropyl) tetrasulfide abbreviated as TESPT of the formula [(C2H5O) 3Si (CH2) 3S2] 2 or the formula [(C2HSO) 3Si (CH2) 3S]. 2 bis (triethoxysilylpropyl) disulfide, abbreviated as TESPD, is used. In addition, as a preferable example, bis (mono (C1-C4) alkoxyldi (C1-C4) as described in International Application No. 02/083782 pamphlet (or US Patent Application Publication No. 7217751). Also included are alkylsilylpropyl) polysulfides (especially disulfides, trisulfides or tetrasulfides), and more particularly bis (monoethoxydimethylsilylpropyl) tetrasulfides.

  As the coupling agent other than the alkoxysilane polysulfide, in particular, WO 02/30939 pamphlet (or US Pat. No. 6,774,255) and WO 02/31041 pamphlet (or US patent application publication 2004/051210). Bifunctional POS (polyorganosiloxane) or hydroxysilane polysulfide (R2 = OH in the above formula (I)), or, for example, WO 2006/125532 pamphlet, Examples include silanes or POS carrying azodicarbonyl functional groups as described in WO 2006/125533 and WO 2006/125534.

  In the rubber composition of the present invention, the content of the coupling agent is preferably between 2 phr and 12 phr, more preferably between 3 phr and 8 phr.

  Those skilled in the art will appreciate that reinforcing fillers having other properties, especially organic, can be filled with the reinforcing fillers either by coating them with an inorganic layer such as silica or by containing functional sites, especially hydroxyl, on their surface. Understand that it can be used as a filler equivalent to the reinforcing inorganic filler described in this section, provided that it requires the use of a coupling agent to form the bond between the agent and the elastomer. Ah

Plasticizer The rubber composition of the present invention has the other essential feature of comprising between 20 and 160 phr of plasticizer, comprising greater than 10 phr and less than 80 phr of vegetable oil. Vegetable oils are, by definition, liquid at 20 ° C.

  The content of essential plasticizer comprising vegetable oils is preferably between 30 phr and 120 phr, more preferably between 40 phr and 100 phr, even more preferably between 50 phr and 80 phr, especially 55. ~ 70 phr. If an essential plasticizer is used in a mixture with other essential plasticizers, the content should be understood as meaning the total content of two or more plasticizers.

  For the content of vegetable oil below the minimum shown, the targeted technical hardening is insufficient. At the maximum shown, there are challenges of cost of vegetable oils and risk of poor processability. For these reasons, the content of vegetable oil is preferably between 10 and 70 phr, more preferably between 15 and 60 phr, even more preferably between 20 and 55 phr.

  Examples of vegetable oils are linseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, turnip seed oil, castor oil, millet oil, pine oil, sunflower oil, palm oil, olive oil, coconut oil, peanut oil, grape seed oil. And an oil selected from the group consisting of mixtures of these oils. Sunflower oil is preferred.

  The vegetable oil may consist primarily of unsaturated C18 fatty acids, ie unsaturated fatty acids selected from the group consisting of oleic acid, linoleic acid, linolenic acid and mixtures of these acids.

  The vegetable oil is preferably rich in oleic acid, ie the fatty acids (or all fatty acids, if several are present) from which the vegetable oil is derived are equal to at least 60%, more preferably at least 70%. It comprises oleic acid in a weight fraction equal to, even more preferably equal to at least 80%, and especially equal to at least 90%.

  As a vegetable oil, all of the fatty acids from which the vegetable oil is derived are in a weight fraction of 60% or more, preferably 70% or more, more preferably 80% or more, and according to one particularly advantageous embodiment of the invention. Sunflower oil comprising oleic acid in a weight fraction of 90% or more is conveniently used.

  The Tg of vegetable oils may, by definition, be below -20 ° C, preferably below -40 ° C.

  Preferably, the plasticizer further comprises a compound selected from the group consisting of liquid plasticizers other than vegetable oils, hydrocarbon resins and mixtures thereof.

  Liquid plasticizers other than vegetable oils, by definition, are liquid at 20 ° C. and their role is to soften the matrix by diluting the elastomer and reinforcing filler. By definition, their Tg is below -20 ° C, preferably below -40 ° C.

  Any extender oil, regardless of aromatic or non-aromatic nature, any liquid plasticizer known for its plasticizing properties for diene elastomers can be used. At ambient temperature (20 ° C.), these plasticizers or their oils are more or less viscous, especially in contrast to the plasticization of hydrocarbon-based resins, which are essentially solid at ambient temperature, in liquid (ie, In the end, it is a substance that has the ability to become the shape of the container.

  Polyolefin oils, naphthenic oils (low or high viscosity, especially hydrogenated or otherwise), paraffin oils, DAE (Distillate Aromatic Extracts) oils, MES (Medium Extracted Solvates) oils, TDAEs (Treated Distillate Erasatric Aromatics, EDA). Aromatic Extracts oil, TRAE (Treatment Residual Aromatic Extracts) oil, SRAE (Safety Residual Aromatic Extracts) oil, mineral oils, ether plasticizers, phosphate plasticizers, ester plasticizers, phosphate plasticizers, sulfonates Plants selected from Liquid plasticizers other than are particularly suitable.

  Phosphate plasticizers may include, for example, those containing between 12 and 30 carbon atoms, such as trioctyl phosphate.

  Ester plasticizers may include, among others, compounds selected from the group consisting of trimellitate, pyromellitate, phthalate, 1,2-cyclohexanedicarboxylate, adipate, azelate, sebacate and mixtures thereof.

  The content of liquid plasticizers other than vegetable oils is preferably 0 phr or less than 20 phr, more preferably less than 15 phr, even more preferably less than 10 phr, especially at most 5 phr.

  Hydrocarbon resins that are solid plasticizers (at 20 ° C.) are, for example, as described in WO 2005/087859, WO 2006/061064 and WO 2007/017060. , Tg higher than + 20 ° C, preferably higher than + 30 ° C.

  Hydrocarbon-based resins are polymers well known to those skilled in the art and are essentially carbon and hydrogen based and therefore inherently miscible in diene elastomer compositions when they are additionally "plasticized". is there. They are described, for example, in R. Mildenberg, M .; Zander and G.G. Collin (New York, VCH, 1997, ISBN 3-527-28617-9), in a work entitled "Hydrocarbon Resins", Chapter 5 (5.5. "Rubber Tires and Mechanical Goods"). )) Describes their use, especially in the rubber field. They can also be of the aliphatic or aromatic, or of the aliphatic / aromatic type, ie they can be based on aliphatic and / or aromatic monomers. They can be natural or synthetic and may or may not be petroleum-based (in which case they are also known by the name of petroleum resin). They are preferably exclusively hydrocarbons, that is to say they comprise only carbon and hydrogen atoms.

Preferably, the "plasticized" hydrocarbon resin has the following characteristics:
Tg higher than 20 ° C (more preferably between 40 ° C and 100 ° C);
A number average molecular weight (Mn) between 400 and 2000 g / mol (more preferably between 500 and 1500 g / mol);
A polydispersity index (PI) lower than 3 and more preferably lower than 2 (note: PI = Mw / Mn; Mw stands for weight average molecular weight)
At least one, and more preferably all.

  Tg is measured in a known manner by DSC (Differential Scanning Calorimetry) according to standard ASTM D3418 (1999). Hydrocarbon resin macrostructures (Mw, Mn and PI) are determined by steric exclusion chromatography (SEC): solvent tetrahydrofuran; temperature 35 ° C .; concentration 1 g / l; flow rate 1 ml / min; 0.45 μm before injection. Solution filtered through a filter having a porosity of; Moore calibration with polystyrene standards; Three "Waters" column sets in series ("Styragel" HR4E, HR1 and HR0.5); Differential refractometer ("Waters 2410") and Detection by its associated operating software ("Waters Empower").

  In a particularly preferred embodiment, the "plasticized" hydrocarbon resin is a cyclopentadiene (abbreviated as CPD) homopolymer or copolymer resin, a dicyclopentadiene (abbreviated as DCPD) homopolymer or copolymer resin, a terpene homopolymer. It is selected from the group consisting of polymer or copolymer resins, C5 cut homopolymer or copolymer resins, C9 cut homopolymer or copolymer resins, alpha-methylstyrene homopolymer or copolymer resins and mixtures thereof. More preferably, among the above-mentioned copolymer resins, (D) CPD / vinyl aromatic copolymer resin, (D) CPD / terpene copolymer resin, (D) CPD / C5 fraction copolymer resin, (D) CPD / C9 fraction. A copolymer resin selected from the group consisting of a copolymer resin, a terpene / vinyl aromatic copolymer resin, a terpene / phenol copolymer resin, a C5 cut / vinyl aromatic copolymer resin, a C9 cut / vinyl aromatic copolymer resin and mixtures thereof. use.

  A “terpene” is a combination of α-pinene monomer, β-pinene monomer and limonene monomer in a known manner herein; preferably limonene monomer is used. This compound exists in known manner in the form of three possible isomers: L-limonene (levorotatory enantiomer), D-limonene (dextrorotatory enantiomer) or dipentene, right. Racemates of the chiral and levorotatory enantiomers. Styrene; α-methylstyrene; ortho-, meta- or para-methylstyrene; vinyltoluene; para- (tert-butyl) styrene; methoxystyrene; chlorostyrene; hydroxylstyrene; vinylmesitylene; divinylbenzene; vinylnaphthalene; or C9. Any vinyl aromatic monomer derived from a cut (or more generally a C8 to C10 cut) is suitable, for example, as a vinyl aromatic monomer. Preferably, the vinyl aromatic compound is a vinyl aromatic monomer derived from styrene or a C9 cut (or more commonly a C8 to C10 cut). Preferably, the vinyl aromatic compound is a micromonomer expressed as the mole fraction in the copolymer considered.

  The content of hydrocarbon resin is preferably between 3 and 60 phr, more preferably between 5 and 50 phr, even more preferably between 10 and 40 phr, especially between 15 and 35 phr.

Water-Soluble Sulfate Microparticles The rubber composition of the present invention has the other essential feature of comprising between 2 phr and 40 phr of alkali metal or alkaline earth metal water-soluble sulfate microparticles.

  Water solubility or solubility in water (it should be noted that it is the maximum weight of a substance dissolved in water at a given temperature and pressure) is basically known for organic or inorganic compounds, and It is one of certain physics (especially available in "Handbooks of Chemistry and Physics").

  It will be appreciated by those skilled in the art that the water-soluble sulfate microparticles are at least partially soluble in water. Preferably, the solubility of the microparticles in water at 0 ° C. under a pressure equal to 1 atmosphere is higher than 1 g / 100 ml, more preferably higher than 2 g / 100 ml and even more preferably higher than 4 g / 100 ml.

  According to a preferred embodiment, the alkali metal or alkaline metal is selected from the group consisting of sodium (Na), potassium (K), magnesium (Mg), calcium (Ca) and mixtures thereof.

  According to a more preferred embodiment, the water-soluble sulphate salt is selected from the group consisting of magnesium sulphate, potassium sulphate and mixtures thereof. Even more preferably, the water soluble sulfate salt is magnesium sulfate.

According to a preferred embodiment, the microparticles are both measured by the laser particle size method according to ISO standard 13320-1, and the following relationships:
−50 μm <D50 <150 μm;
-0.50 <span <1.50;
Has a specific median particle size (D50) by volume and a specific width (span) of the volume particle size distribution.

  D50 is the median particle size (diameter) by volume corresponding to 50 (volume)% of the cumulative distribution obtained from the volume particle size distribution, that is, the particle size by volume, and the diameter at which 50% of the minute particle size is smaller than D50. , And another 50% of the fine particle size has a diameter greater than D50. It is preferred that the D50 is between 75 μm and 125 μm as it provides an optimal compromise between the desired surface roughness and proper contact between the rubber composition and the ice.

The span, the width of the volume particle size distribution, is measured in a known manner and is defined by the following equation:
-Span = (D90-D10) / D50
Preferably the span is between 0.75 and 1.25.
Here, D10 and D90 are diameters (particle diameters) of fine particles corresponding to 10 (volume)% and 90 (volume)% of the cumulative particle distribution, respectively.

  According to another preferred embodiment, D10 is greater than 30 μm, more preferably greater than 40 μm and especially greater than 50 μm.

  According to another preferred embodiment, combined or not combined with the above embodiments, the D90 is less than 180 μm, more preferably less than 160 μm, especially less than 150 μm.

  In addition, the content of microparticles in the rubber composition according to the invention in order to obtain an optimal compromise between targeted technical effect (production of suitable microroughness), grip performance on melt ice and cost Is preferably between 2 and 30 phr, more preferably between 5 and 20 phr.

  The particle size distribution by volume (i.e. volume particle distribution) is characterized by a laser particle size analyzer according to ISO standard 13320-1 (1999) in a known manner, unless explicitly stated otherwise.

  HORIBA Co. A "Partica LA-950V2" Laser Diffraction Particle Size Analyzer with its data processing software (P2000704001H version 4.11), provided by Dr. The programming parameters of the measurement are as follows: use of Fraunhofer model; no initial sample treatment by ultrasound; tank circulation speed: 6 (corresponding to about 1400 rpm); cell agitation speed: 6 (ie, Red laser (650 nm); Focal length from subject: 450 mm; Initial alignment control of laser and measurement of background noise (tank containing ethanol).

  A suspension of the sample to be tested is first prepared: for this purpose approximately 500 mg of the sample is placed in an empty beaker (volume approximately 100 ml) and then using a few drops of ethanol dropped at 95 °. , Wet the sample and form a paste with a toothpaste consistency; finally, 40 ml of ethanol are added to this preparation, which is then applied for about 15 seconds with a bar magnet and a magnetic stirrer. (Magnetic stirrer IKA (registered trademark) "RET BASIC", graduation 750) is used for stirring.

  The resulting suspension was then pipetted into a tank of the particle sizer preparation initially loaded with 95 ° ethanol (low level, ie about 180 ml) (optimum). Inject to the obscuration level of the measuring cell indicated on the device between 15% and 20% (corresponding to the concentration).

  The measurement is carried out immediately after the stabilization of the obscuration level, and in order to control reproducibility, three consecutive measurements are carried out on the same preparation. In order to demonstrate this first measurement, a new preparation (suspension) is made and analyzed according to the same protocol: the two measurements must be identical (reproducibility according to the standard recommendations) . After preparation and measurement, respectively, the cell and tank for preparation in the laser particle size analyzer are rinsed twice with deionized water.

  The recorded data are finally used by the software to produce the volume particle size distribution curve and the desired characteristics of the volume distribution (D10, D50, D90 and span).

Various Additives The rubber compositions of the present invention include, for example, protective agents such as anti-ozone wax, chemical antiozonants, antioxidants, toughening resins, methylene acceptors (eg, phenol novolac resins) or methylene donors. Tires, in particular for winter, such as (for example HMT or H3M), sulfur and / or sulfur donors and / or crosslinking systems based on peroxides and / or bismaleimides, accelerators or vulcanization activators It also comprises all or part of the useful additives commonly used in elastomeric compositions intended for the manufacture of treads for tires.

  These compositions are, if coupling agents are used, coupling activators, agents that convert inorganic fillers, or more generally, improve the dispersion of fillers in a rubber matrix in a well known manner. It may also contain a crosslinking aid which is capable of reducing the viscosity of the above and improving the processing characteristics of the raw material state. These agents are, for example, alkylalkoxysilanes, polyols, polyethers, amines or hydrolyzable silanes such as hydroxylated or hydrolyzable polyorganosiloxanes.

Manufacture of rubber compositions and treads The rubber compositions of the invention are prepared in suitable mixers according to the general procedure well known to the person skilled in the art in two successive production stages: between 130 and 200 ° C, preferably between 145 and 185. A first stage of thermo-mechanical working or kneading (sometimes referred to as a "non-production" stage) at elevated temperatures up to a maximum temperature of between 0 ° C and subsequent temperatures, typically below 120 ° C, eg 60 Manufactured using a second machining stage (described as the "production" stage) at low temperatures between 0 ° C and 100 ° C, which incorporates a crosslinking or vulcanization system in its finishing stage.

Processes that can be used for the production of such compositions, for example, preferably include the following steps:
During the first stage (the "non-production" stage), incorporating the reinforcing filler, the plasticizer comprising vegetable oil, the microparticles in the diene elastomer in a mixer, all once Or more, thermomechanically kneading until a maximum temperature of between 130 ° C and 200 ° C is reached;
Cooling the mixture to a temperature below 100 ° C .;
Then, during the second stage (“production” stage), incorporating a cross-linking system;
Kneading everything to a maximum temperature of less than 120 ° C;
Extruding or calendering the rubber composition so obtained, especially in the form of a tire tread.

  By way of example, the first (non-production) stage is carried out in a single thermomechanical step during which all essential components, any additional coating or processing aids and crosslinking system are removed. Various other additives are introduced into a suitable mixer, such as a standard internal mixer. After cooling the mixture thus obtained during the first non-production stage, the crosslinking system is introduced at low temperature into an external mixer, typically an open mill. Then everything is mixed for a few minutes, for example between 5 and 15 minutes (second (production) stage).

  Suitable crosslinking systems are preferably based on sulfur and primary vulcanization accelerators, especially accelerators of the sulfenamide type. To this vulcanization system, various known secondary accelerators or vulcanization activators such as zinc oxide, stearic acid, guanidine derivatives (especially diphenylguanidine), etc. are added, during the first non-production stage and / Or mix during the above production steps. The sulfur content is preferably between 0.5 phr and 3.0 phr and the content of primary accelerator is between 0.5 phr and 5.0 phr.

  The accelerator (primary or secondary) may be any compound capable of acting as a vulcanization accelerator for diene elastomers in the presence of sulfur, especially those of the thiazole type and its derivatives, thiuram type. Accelerators, or zinc dithiocarbamate may be used. These accelerators are more preferably 2-mercaptobenzothiazyl disulfide (abbreviated as "MBTS"), N-cyclohexyl-2-benzothiazole sulfenamide (abbreviated as "CBS"), N, N-dicyclohexyl-2-benzothiazolesulfenamide ("DCBS"), N-tert-butyl-2-benzothiazolesulfenamide ("TBBS"), N-tert-butyl-2-benzothiazolesulfenimide ( “TBSI”), zinc dibenzyldithiocarbamate (“ZBEC”) and mixtures of these compounds.

  The final composition thus obtained is then calendered, for example in sheet or plaque form, in particular for laboratory characterization, or else can be used directly, for example as a winter tire tread. Extrude in the form of shape elements.

  Vulcanization (or curing) is carried out in a known manner, generally at temperatures between 130 ° C. and 200 ° C., depending in particular on the curing temperature, the vulcanization system used and the vulcanization rate of the composition considered. , For example, for a sufficient time that can vary between 5 and 90 minutes.

  The rubber composition according to the invention may, in the case of a composite type tread formed from several rubber compositions of different formulations, constitute all or only part of the tread according to the invention.

  The present invention relates to the above rubber composition and tread both in the raw state (ie before curing) and in the cured state (ie after crosslinking or vulcanization).

  The present invention is further described by the following non-limiting examples.

Preparation of rubber compositions and treads The following tests were carried out in the following manner: reinforcing fillers (eg reinforcing inorganic fillers such as silica and related coupling agents), plasticizers, microparticles, diene elastomers (or The diene elastomer blend) and various other ingredients except the vulcanization system are continuously introduced into an internal mixer having an initial vessel temperature of about 60 ° C .; therefore, the mixer is about 70% full. (volume%). Thermomechanical processing (non-production stage) was then carried out in one stage lasting a total of about 3-4 minutes until the maximum "fall" temperature of 165 ° C was reached. The mixture so obtained is regenerated, cooled and then the sulfur and sulfenamide type promoters are admixed at 30 ° C. in an external mixer (homofinisher), all for a suitable time (eg Mixed (between 5 and 12 minutes) (production stage).

  The compositions thus obtained are then in the form of rubber sheets (thickness of 2-3 mm) or fine sheets or to the desired dimensions for the determination of their physical or mechanical properties. After cutting and / or assembling, it was calendered into any of the forms of the form elements which can be used directly, for example as tire semifinished products, in particular as tire treads.

Friction Tests In these tests, five compositions based on diene elastomers (BR and NR blends comprising a content of cis-1,4 bonds higher than 95%) (C-1, C-2, (Identified as C-3, C-4 and C-5) are compared. These five compositions were reinforced by a blend of silica and carbon black and in combination with some (10 phr) magnesium sulfate particles (as microparticles of alkali metal or alkaline earth metal water soluble sulfate salts). Or a plasticizer with or without 55 phr or 20 phr of oleic sunflower oil (as vegetable oil), or not. The microparticles were obtained by suitable filtration as shown in WO 2012/052331 A and equipped with its data processing software (P200070401H version 4.11 provided by HORIBA Co., Ltd.). It has a specific volume distribution defined by D50, span (also D10 and D90) as measured by laser diffractometry (according to "Partica LA-950 V2").
Composition C-1: vegetable oil-free, microparticle-free composition (reference);
Composition C-2: Composition not containing vegetable oil but containing fine particles (Comparative Example);
Composition C-3: Composition not containing vegetable oil but containing fine particles (Comparative Example);
Composition C-4: A composition according to the invention comprising 55 phr of vegetable oil and comprising microparticles;
Composition C-5: A composition according to the invention comprising 20 phr of vegetable oil and comprising microparticles;

  The formulations of the five compositions (contents of various products represented in Table 1-phr) and their ice rub results are shown in Tables 1 and 2. The vulcanization system is composed of sulfur and sulfenamide.

  Laboratory tests were performed on these five compositions, which consisted of measuring their coefficient of friction on ice. The principle is based on a block of rubber composition sliding at a given speed (e.g. equal to 5 km / hour) on an ice track with an applied load (e.g. equal to 3 kg / cm2). The force (Fx) generated in the traveling direction of the block and the force (Fz) generated in the direction perpendicular to the traveling direction of the block are measured. The Fx / Fz ratio determines the coefficient of friction of the test piece on ice. The temperature during the measurement is set to -2 ° C. The surface of the block of the rubber composition according to the invention which comes into contact on ice was cut into fine pieces of rubber about 0.5 mm before the rubbing test in order to expose the fine particles on the surface.

  This test, the principle of which is well known to the person skilled in the art (see, for example, European Patent Application Nos. 1052270 and 1505112), was used to load tires in which the tread is composed of the respective rubber composition. It makes it possible to evaluate, under typical conditions, the grip on ice in the temperature range between 0 ° C. and −5 ° C. that would be obtained after running tests in a conditioned vehicle.

  The results are shown in Table 2. Values higher than the value of the reference (Composition C-1), arbitrarily set to 100, show improved results, i.e. induced suitability for shorter braking distances, i.e. the higher the value the ice grip Is also good. C-4 and C-5 according to the invention have a significant or specific increase in the coefficient of friction at -2 ° C compared to reference composition C-1 and comparative examples C-2 and C-3. Are observed in Table 2.

Dynamic Properties Each of the above five compositions was tested to determine their dynamic properties in viscosity (Metravib VA4000) according to standard ASTM D5992-96. A sample of a vulcanized composition (cylindrical specimen with a thickness of 4 mm and a cross section of 400 m2) subjected to a simple alternating sinusoidal shear stress at a frequency of 10 Hz during a temperature sweep under a constant stress of 0.7 MPa. Was recorded. The tan (δ) value observed at 0 ° C was recorded. The ratio of tan (δ) 0 ° C. of the example (or comparative example) to the reference, arbitrarily set to 100, in a manner well known to those skilled in the art, represents the gripping potential of wet road surfaces, the higher the ratio, the higher the reference. It should be remembered that a better wet grip is obtained.

  The results of the ratio are shown in Table 2. It has been found that the composition C-2 according to the invention shows significantly higher values than the reference composition C-1 and the comparative examples C-2 and C-3. Another example composition C-4 has similar values in terms of wet grip as reference C-1, comparative examples C-2 and C-3.

  In conclusion, the results of the above tests show that the rubber composition according to the invention with a plasticizer comprising vegetable oil and fine particles of water-soluble sulphate of an alkali metal or alkaline earth metal maintains the wet grip performance of a tire or Further and while improving, it gives tires and their treads good ice grip performance, in particular melt ice grip performance.

Claims (10)

at least,
A diene elastomer,
-Reinforcing filler between 60 and 120 phr ,
Between 40 and 100 phr of plasticizer, comprising greater than 10 phr and less than 80 phr of vegetable oil;
A rubber composition comprising between 2 phr and 40 phr of water-soluble sulphate microparticles selected from the group consisting of magnesium sulphate, potassium sulphate and mixtures thereof.   The vegetable oil is linseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, turnip seed oil, castor oil, tung oil, pine oil, sunflower oil, palm oil, olive oil, coconut oil, peanut oil, grape seed oil and them. The rubber composition according to claim 1, which is selected from the group consisting of a mixture of The said microparticles are both measured by laser diffractometry according to ISO standard 13320-1, and the following relations:
−50 μm <D50 <150 μm;
-0.50 <span <1.50;
(Where D50 is the median particle size by volume corresponding to 50% of the cumulative distribution obtained from the volume particle size distribution;
Span = (D90-D10) / D50; and D10 and D90 are the particle sizes corresponding to 10% and 90% by volume of the cumulative particle distribution, respectively, and the median particle size and volume particle by volume. The rubber composition according to claim 1 or 2, which has a width of a diameter distribution.   The rubber composition according to any one of claims 1 to 3, wherein the alkali metal or the alkaline earth metal is selected from the group consisting of sodium, potassium, magnesium, calcium and a mixture thereof.   The rubber composition according to any one of claims 1 to 4, wherein the water-soluble sulfate salt is selected from the group consisting of magnesium sulfate, potassium sulfate, and a mixture thereof.   The rubber composition according to any one of claims 1 to 5, wherein the diene elastomer is selected from the group consisting of natural rubber, synthetic polyisoprene, polybutadiene, butadiene copolymer, isoprene copolymer and mixtures thereof.   7. A rubber composition according to any one of claims 1-6, wherein the reinforcing filler comprises more than 70 phr of a reinforcing inorganic filler.   The rubber composition according to any one of claims 1 to 7, wherein the plasticizer further comprises a compound selected from the group consisting of a hydrocarbon resin, a liquid plasticizer other than the vegetable oil, and a mixture thereof. .   The rubber composition according to claim 9, wherein the content of the liquid plasticizer other than the vegetable oil is less than 20 phr. A tread for pneumatic tires, comprising the composition according to any one of claims 1-9.